What is the formula for compression ratio?

What is the formula for compression ratio?

• A. (original size / compressed size) : 1
• B. (compressed size / original size) : 1
• C. (original size - compressed size) : 1
• D. (original size + compressed size) : 1

Answer: (A)

Compression ratio shows how many times bigger the original data is compared to its compressed form. It is found by dividing the original size by the compressed size, which is written as (original size ÷ compressed size) : 1, or equivalently as original:compressed. For example, if a file goes from 1000 bytes to 250 bytes, the ratio is 1000 ÷ 250 = 4, written as 4:1. This means the data is four times smaller after compression. The other expressions don’t describe the reduction: inverted by using compressed/original would give the reciprocal ratio; subtracting the sizes gives the amount saved, not the ratio; adding the sizes isn’t a ratio at all.

Compression ratio shows how many times bigger the original data is compared to its compressed form. It is found by dividing the original size by the compressed size, which is written as (original size ÷ compressed size) : 1, or equivalently as original:compressed.

For example, if a file goes from 1000 bytes to 250 bytes, the ratio is 1000 ÷ 250 = 4, written as 4:1. This means the data is four times smaller after compression.

The other expressions don’t describe the reduction: inverted by using compressed/original would give the reciprocal ratio; subtracting the sizes gives the amount saved, not the ratio; adding the sizes isn’t a ratio at all.